The driveshaft specialist you talked with may know how to weld shafts together but I believe he gave you some bad info on driveshaft angles. I defiantly wouldn’t set the driveshaft level with all the adjustment coming out of the pinion. As stated by Dan and Jerry you need to check the angles on both the trans and pinion and work from there. As stated before there are a lot of trans yokes out there, mine included that have clearance reliefs in them. Link below to a simplified way to set up. Set up the angles then see if it still binds, grind clearance reliefs in it and if it vibrates take it out and have it balanced.
Drive Shaft Harmonics
Paul T.